Exploring the influence of calendering and coating line conditions on the microstructure of cathode electrode in lithium-ion batteries: Ultrasonic testing insights

Lithium-ion batteries require high-density, uniform cathodes for efficient energy storage and manufacturing with minimal waste. Ensuring consistent cathode quality during manufacturing while avoiding the production line-related wastes remains as critical obstacle. Non-destructive diagnostic methods are vital for detecting inconsistencies and understanding parameter impacts during production. Ultrasonic testing (UT) offers precise insights into microstructure and its correlation with parameters such as line speed, coat weight and calendering. This study leverages UT to investigate the impact of key parameters including coat weight (141, 182, and 218 gsm), line speed (0.5 and 1 m/min), and roll gap (432, 477, and 522 μm)—on cathode microstructural properties. The results show that high coat weights lead to longer time of flight (ToF, μs) and reduced amplitude (a.u.), indicating increased internal attenuation, higher coat weights, such as 218 gsm, exhibited a 12 % increase in ToF and 15 % decrease in amplitude, reflecting greater compaction and reduced porosity. Slower line speed (0.5 m/min) led to faster ToF and higher amplitude, reflecting improved material uniformity due to extended processing time. Smaller roll gaps during calendering enhanced consistency, faster ToF, and increased amplitudes across multiple locations, signifying improving compactness and structural uniformity. • Acoustic/Ultrasonic Inspection of NMC cathode manufacturing process. • Microstructural alterations during coating and calendering. • Optimization of NMC cathode manufacturing process parameters. • Initial attempt to digitalise battery manufacturing.